Let us Stop and Summarize
• The amount of noise is generally fixed by the design of the transformer.
• Adjustments to a design to reduce the noise level can be made at cost but don't
expect a huge reduction in the noise level
• Loading a transformer has little effect on the noise level.
• Vibrations are produced as well as noise and these are just as important as the noise.
There are three basic categories currently in use:
• Those immersed in liquids - oils, silicones, etc.
• Those immersed in vapors and gases – nitrogen, fluro-carbons, etc.
• Those mounted in air.
A basic statement can be that irrespective of how transformer core and coils are surrounded, noise and vibration will still be transmitted. Oil is incompressible, and gas and air, we know, transmit sound very effectively. Until we put units in absolute vacuums, we have to accept that they will transmit sound almost as if all were in air.
However, each type requires special consideration and treatments, and it is important that these are understood. Transformer size, requirements, and it is important that these are understood. Transformer size, requirements and applications will determine more exactly where and how a transformer is placed, but there are certain treatments which are common to all type. First, let us consider how transformer noise is measured.
